This is a walkthrough of the Crypt Of Hearts section of TESI: Arena. Providing some lore, I thought it would also be a good start for ideas regarding the look and layout of the Crypt Of Hearts, and surrounding area.
The Shadowkey version of the Crypt of Hearts is set in 3E 397 so I chose to write about the Arena version as it is closest to our date, however i do think certain aspects of Shadowkey could be interesting to include if they do not conflict with later accounts, such as aesthetics.

ARENA 3E 399 (so 28 years before 3E 427)

Ria Silmane visits you after recovering the 5th piece of the Staff of Chaos
"It has become a habit, congratulating you on your success. Still, there are three pieces left, and what guards them only the Divine Lady may know. I have spent many a day searching the ethereal planes for some clue as the location of the sixth piece of the Staff. This is what I have found. The piece was sent to a place called the Crypt of Hearts. I have no clue as to the location of such a place. The price for the little knowledge I have was... exacting. Still, only three provinces remain that can hold these last pieces. It can only lie in one of these. Good luck..."

After speaking to someone about the Crypt of Hearts they will tell you to visit the temple of the Brotherhood of Seth in Camlorn.

When you enter the Brotherhood of Seth in Camlorn for the first time there is only one guy to talk to, he offers temple services: bless, heal and cure
(in game text)
'I welcome you to the Brotherhood of Seth (player name). Word of your inquiries concerning the Crypt of Hearts has come to my attention. I am Halfas Varn, senior brother in this temple. I would gladly help you on your quest, but dire times are upon us. One of out brethren, Barnabas of Tethis, went mad raving that the Emperor had been captured. He insisted that only something called the Staff of Chaos could free the Emperor from his fate. Naturally we did not believe him, he was ever one live in fanciful dreams. Instead we tried our best to soothe him, talking to him of brighter, happier things. We thought he was fine. Yesterday afternoon he went berserk and killed brother Martinus, then fled from the temple. With him he took a scroll that he claimed would help him find a piece of the missing so-called Staff of Chaos. I fear he has gone to the Mines of Khuras, the place where he claimed the map said he would find his first clue. What he doesn't realize is that the map he carries was originally found in the Mines. Part of the inscription on the map is a code that we planned to use to decipher the location of the Crypt of Hearts from the Elder Scrolls. Without that map we haven't a chance. If only there was a way of recovering the map but the Mines of Khuras are too dangerous. Poor brother Barnabus has surely perished by now. I will tell you how to get to the Mines. There you can search for the map or for brother Barnabus. I think it unlikely that you will find either but there is always a slim chance. If you return to me with the map I will tell you the location of the Crypt of Hearts. It is a fools errand but such is your only hope. Do you wish to search the Mines? Yes/No.
Yes
I had thought you would decline faced with the danger of the Mines. Lava pools and fire pits are scattered throughout its scorched corridors. You must find something to protect you from the heat of its fires. Hopefully you will find both brother Barnabus and the map. No matter, the Mines of Khuras are located near Camlorn. If you find the map return here to the Brotherhood of Seth. I will tell you the location of the Crypt of Hearts.'
Brother Halfas gestures and you see on your map the location of the Mines of Khuras magically appear...

OK, so travelling from Camlorn to the Mines takes around five days (Arena time) and the total distance travelled is 200km. The Mines are a two-storey huge dungeon.

When you enter the Mines
(in game text)
'The sulphuric air of the Mines of Khuras hits you like a wall of heat, bringing tears to your eyes. Through the shimmering air you can see numerous lava flows and pits that lie scattered about the scorched ground, treacherous and deadly...'

Near the entrance you find a dead body containing 35 gold and a long bow
(in game text)
'This body you summarise is that of an unlucky adventurer. The flesh seems torn and perhaps chewed. Scrawled in blood on the floor next to it are the letters SW...'

The Mines contain spiders, skeletons, these black jaguar shaped creatures with red eyes that spit fireballs (called a tiger in game but really does not look like one), iron golems, stone golems, red winged imp-like creatures, ghosts, one fire daedra boss and treasure. There are also several traps, like fire pits and secret doors which lead to rooms filled with treasure.

On a wall within the Mines
(in game text)
'Scratched into the wall is a short message, Ware the Emperor, his minions await me. A strange message to find within these depths...'
When walking around the Mines
(in game text)
'Gauges and scrapes in the rock here seem to indicate that something big passed by here not too long ago...'
(in game text)
'Around you lie pools of seething lava, welling up from deep below and releasing their gases into the air, which seems tainted but breathable...'

On the second floor of the Mines you find a dead body in priest robes
(in game text)
'This body is obviously that of brother Barnabus. His body has been ravaged by the denizens of this underdark and his face etched into a mask of pure terror. Just beyond the body you can see what looks like a map...'
Next to him is a piece of parchment
(in game text)
'You have found the map fragment only slightly discoloured by brother Barnabus' blood. With the help of the Brotherhood of Seth you may succeed where Barnabus failed...'

OK after leaving the Mines and returning to Camlorn and the Brotherhood of Seth
(in game text)
'Unbelievable. I did not credit you with the tenacity you obviously possess. For my part I gave my word to tell you the location of the Crypt of Hearts and Gods do not suffer men whose words carry no weight. Hold a moment while I read this map...'
Brother Halfas takes the map you recovered and goes into another room. Almost an hour goes by before he returns. He nods knowingly to you and asks for your map. Quickly he sketches out the location of the Crypt of Hearts somewhere in High Rock province.

So from Camlorn to the Crypt of Hearts it takes around 19 days and is 840km.The Crypt of Hearts is actually a four storey dungeon.

'The chill of death seems to touch your heart as you gaze upon the stone walls of the Crypt of Hearts. Above the entrance stands a grinning skull, a warning to those who would traverse the halls of the dead. You can sense the sixth piece of the Staff of Chaos somewhere below...'

Upon entering the Crypt
(in game text)
'You stand in the Crypt of Hearts, a world of darkness and death. The air is still, decayed with age, and the smell of sulphur pervades the air. A hot wind seems to be coming from around the corner, to the south...'

Within the Crypt are stone carvings of the moons and a dragon along the walls (one in the first room is a secret doorway). There are several what look like small deadric shrines (to lesser daedra) within the Crypt along with several dead bodies, candles, occult symbols on the walls et cetara. There are the same creatures, traps, and treasure as found in the Mines along with the addition of vampires. There are also lava pits but no where near to the extent as the Mines.

On the lower levels
(in game text)
'From somewhere comes the smell of sulphur and along with it a blast of hot air...'

You then come to a door which leads to the room the piece is in
(in game text)
'Few have gained these hallowed halls, brave fools who wouldst face the puzzle
There is a thing, which nothing is,
Yet it has a name,
Its sometimes tall,
And sometimes short,
It tumbles when we fall,
It joins our sport,
And plays at every game.
What then doth I speak of?'
Answer - shadow
'Thou art correct mortal, proceed to thy fate'
Inside the room are two fire daedra.

You can then leave the Crypt of Hearts and Ria Silmane will appear to you again and tell you about the next piece of staff.